Hand-held scanners work best for scanning small images. However, you must have a steady hand when moving the scanner across the page. Otherwise, you will get fuzzy images on your monitor. These generally attach to a serial port on your PC.
The flatbed or desktop scanner can scan a page at a time. You simply lift the lid of the scanner, and put the sheet in. You tell the scanning software that you are ready to scan and it does the rest.
Desktop scanners work best for scanning pages. These generally scan images more clearly than the hand-held scanner. These come with their own expansion card for installation.